What antibiotic is recommended for a 5‑month‑old infant with a two‑week cough and no other signs of bacterial infection?

Antibiotics Are Not Recommended for a 5-Month-Old with Two Weeks of Isolated Cough

For a 5-month-old infant with cough lasting two weeks and no other symptoms, antibiotics should not be prescribed at this time. The cough must persist beyond four weeks before antibiotic therapy is indicated, and only if the cough is wet/productive in character. 1, 2

Why Antibiotics Are Not Indicated Now

• The two-week duration does not meet the threshold for chronic cough. Chronic cough is defined as lasting more than four weeks, which is when protracted bacterial bronchitis (PBB) becomes a diagnostic consideration and antibiotics are recommended. 1, 3

• Most acute viral coughs in infants resolve within 1-3 weeks, with 90% of children cough-free by day 21 (mean resolution 8-15 days). 2 At two weeks, this infant is still within the expected timeframe for viral illness resolution.

• The absence of other symptoms argues strongly against bacterial infection. There are no "specific cough pointers" such as coughing with feeding, respiratory distress, failure to thrive, digital clubbing, high fever (≥39°C), or signs of pneumonia that would warrant immediate antibiotic therapy. 1, 3

Current Management Approach

Supportive care is the appropriate management:

• Ensure adequate hydration to help thin secretions. 2
• Gentle nasal suctioning if congestion is present. 2
• Maintain a supported sitting position to help with breathing. 2
• Use antipyretics (acetaminophen) only if fever is causing discomfort, not to lower temperature alone. 2

Critical safety warning: Over-the-counter cough and cold medications should never be used in children under 2 years due to lack of efficacy and serious toxicity risk, including 43 reported deaths in infants under 1 year from decongestants alone. 2

When to Reassess for Antibiotics

At four weeks of persistent cough, if the cough becomes wet/productive:

• Initiate a 2-week course of antibiotics targeting common respiratory bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis). 1, 3
• First-line antibiotic choice: Amoxicillin 90 mg/kg/day divided into two doses, or amoxicillin-clavulanate (amoxicillin component 90 mg/kg/day) if the child is not fully immunized or has recently received antibiotics. 1, 2, 4

Red Flags Requiring Immediate Medical Evaluation

Seek urgent medical attention if the infant develops:

• Respiratory rate >70 breaths/min. 2
• Difficulty breathing, grunting, or cyanosis. 2
• Oxygen saturation <92% (if measured). 2
• Not feeding well or signs of dehydration. 2
• Persistent high fever ≥39°C for 3+ consecutive days. 2, 3
• Any specific cough pointers (coughing with feeds, respiratory distress). 1, 3

Common Pitfalls to Avoid

• Do not prescribe antibiotics empirically for acute cough <4 weeks duration in the absence of signs of bacterial pneumonia or other specific bacterial infection. 2, 3, 5
• Do not use the color of nasal discharge to distinguish viral from bacterial infection—purulent rhinitis can persist up to two weeks with viral infections and does not indicate bacterial infection. 2, 5
• Do not obtain a chest radiograph unless the infant develops signs of severe bacterial infection, respiratory distress, or hypoxia, as routine imaging in uncomplicated respiratory infections is non-specific and unhelpful. 2

Follow-Up Timeline

• Review at 48 hours if symptoms are deteriorating or not improving. 2
• Reassess at 4 weeks if cough persists—this is when the diagnosis transitions to chronic cough and systematic evaluation (including chest radiograph and consideration of antibiotics for wet cough) becomes appropriate. 1, 2, 3